1. Field of the Invention
The present invention relates to a photographing optical lens assembly, and more particularly, to a compact photographing optical lens assembly used in a camera mobile phone.
2. Description of the Prior Art
In recent years, with the popularity of camera mobile phones, the demand for compact photographing lenses is increasing, and the sensor of a general photographing camera is none other than CCD (charge coupled device) or CMOS device (Complementary Metal Oxide Semiconductor device). Furthermore, as advanced semiconductor manufacturing technology has allowed the pixel size of sensors to be reduced and electronic devices have become more compact and powerful, there is an increasing demand for compact photographing lenses featuring better image quality.
In order to correct aberrations, a conventional mobile phone lens assembly usually takes the form of a triplet lens design, with the most commonly seen triplet type being positive, negative and positive. However, when the volume of the lens assembly is reduced, less space is available for the image forming system, making it difficult to fit the three lenses in the limited space. Therefore, the thickness of the lenses must be reduced, resulting in plastic-injection-molded lenses which have poor material homogeneity.
The miniaturized optical lens assembly disclosed in U.S. Pat. No. 7,463,433 comprises two plastic lens elements with refractive power, that is, a first lens with positive refractive power, and a second lens with negative refractive power are arranged in order from the object side to the image side. Though such an arrangement enables the optical lens assembly to obtain good resolution and maintain a compact form, but because the first lens is specified with two convex surfaces, the refractive power of each lens in the system has to be relatively stronger, resulting in an increase in the sensitivity of the optical system. Therefore, it may be difficult to control the yield of the lens assembly.